Active Intellect

The active intellect (Latin: intellectus agens; also translated as agent intellect, active intelligence, active reason, or productive intellect) is a concept in classical and medieval philosophy. The term refers to the formal (morphe) aspect of the intellect (nous), in accordance with the theory of hylomorphism.

The nature of the active intellect was the subject of intense discussion in medieval philosophy, as various Muslim, Jewish and Christian thinkers sought to reconcile their commitment to Aristotle's account of the body and soul to their own theological commitments. At stake in particular was in what way Aristotle's account of an incorporeal soul might contribute to understanding of the nature of eternal life.

The idea is first encountered in Aristotle's De Anima, Book III. Following is the translation of one of those passages (De Anima, Bk. III, ch. 5, 430a10-25) by Joe Sachs, with some notes about the Greek:

...since in nature one thing is the material (hulē) for each kind (genos) (this is what is in potency all the particular things of that kind) but it is something else that is the causal and productive thing by which all of them are formed, as is the case with an art in relation to its material, it is necessary in the soul (psuchē) too that these distinct aspects be present;

the one sort is intellect (nous) by becoming all things, the other sort by forming all things, in the way an active condition (hexis) like light too makes the colors that are in potency be at work as colors (to phōs poiei ta dunamei onta chrōmata energeiai chrōmata).

This sort of intellect [which is like light in the way it makes potential things work as what they are] is separate, as well as being without attributes and unmixed, since it is by its thinghood a being-at-work, for what acts is always distinguished in stature above what is acted upon, as a governing source is above the material it works on.

...
Wikipedia